1. Field of the Invention
The present invention relates to a system for controlling an oil pressure of a transmission which is hydraulically activated to set a gear ratio properly.
2. Related Art
Oil pressures to be used in the transmission are one for activating valves and one for transmitting a torque. The latter oil pressure necessary for the torque transmission is demanded to have a considerably high level but may correspond to the torque to be transmitted. In the vehicular transmission having a hydraulically controlled transmission mounted thereon, therefore, the oil pressure to be generated is varied according to the torque so that it may not become excessively high to prevent the fuel economy from deteriorating.
For example, a continuously variable transmission is constructed to have continuously variable gear ratios such that transmission members such as belts or power rollers are continuously varied in their radial positions for frictional contacts by utilizing that the peripheral velocities of rotary members are different according to those radial positions. In the continuously variable transmission of this kind, the torque is transmitted by frictional forces so that the frictional forces may match the torque to be transmitted, by varying the oil pressure for generating the frictional forces according to the toque. More specifically, the oil pressure is controlled on the basis of engine loads, as represented by the opening of a throttle or the opening (or depression) of an accelerator (pedal).
One example will be described on a belt-type continuously variable transmission. In the transmission of this kind, the torque is transmitted through the frictional forces which are generated between driving and driven pulleys having variable groove widths and a belt made to run on the pulleys. For this torque transmission, therefore, the belt clamping force by the pulleys is controlled on the basis of a load (e.g. accelerator depression) of a prime mover such as the engine connected to an input side of the continuously variable transmission.
As the control for generating the belt clamping force with the oil pressure, there has been known the so-called xe2x80x9copen loop controlxe2x80x9d, in which a target oil pressure and clamping force are obtained by outputting an instruction signal based on the load and by activating a control device such as a solenoid valve in response to that instruction signal. One example of the open loop control is disclosed in Japanese Patent Laid-Open No. 9-217800. This hydraulic control system is constructed such that the line pressure is modulated to the oil pressure of an instruction signal for a controller. In order to prevent the individual difference of the control part such as a solenoid from influencing the oil pressure, on the other hand, a detecting oil pressure is generated in response to an indication from the controller and is detected in terms of ON of a hydraulic switch disposed in a line pressure circuit, so that the correction of a working pressure may be learned and controlled on the basis of a signal coming from the hydraulic switch. Moreover, the detecting oil pressure is preferably generated under conditions for exerting no influence upon the actions of the transmission. These conditions are exemplified by the idling time, the N-range, the normal oil temperature or the vehicle stop.
The aforementioned hydraulic control system of the prior art can be made at a reasonable cost because the oil pressure sensor is replaced by a hydraulic switch, and can prevent the durability from being lost by the high oil pressure because the detecting oil pressure is temporarily generated at the idling time in the N-range or the like where the power is not transmitted to the continuously variable transmission. In that hydraulic control system of the prior art, however, one specific oil pressure is employed as the detecting oil pressure by using the hydraulic switch in place of the oil pressure sensor. This makes it probable that the learning correction cannot always be precisely made on the oil pressure over a wide practical range.
In an electrically activated hydraulic device such as a linear solenoid, on the other hand, there may be a difference between the characteristics in the pressure rising process and the characteristics in the pressure falling process. With a large characteristic difference or hysteresis, the oil pressure cannot be precisely controlled. Moreover, the hydraulic control system of the prior art is constructed to detect one specific oil pressure with the switch. This construction makes it disadvantageously impossible to detect the width of the hysteresis.
An object of the invention is to provide a hydraulic control system capable of learning and correcting properly the instruction value of an oil pressure to be used in the transmission.
Another object of the invention is to provide a control system capable of learning and correcting the oil pressure without affecting the active state of the transmission adversely.
A first feature of the invention resides in that the rotating speed of a prime mover connected to a hydraulic pump is raised with the transmission being stopped, in that instruction signals for generating a plurality of oil pressures is outputted in the stop state, in that the oil pressures corresponding to the individual instruction signals, and in that the instruction value of the oil pressure is learned and controlled on the basis of the detection result. On the other hand, a second feature of the invention resides in that the instruction signals for generating the plurality of oil pressures are outputted, in that the oil pressures corresponding to the individual instruction signals are detected, and in that the instruction values of the oil pressures are learned and controlled on the basis of the detection results.
According to the invention, more specifically, there is provided a hydraulic control system for generating an oil pressure by turning a prime mover connected to a hydraulic pump and for outputting an oil pressure instruction signal to an electrically activated pressure modulating mechanism, to modulate the oil pressure generated in the hydraulic pump to an oil pressure according to the instruction signal and to feed the modulated oil pressure to a transmission. The hydraulic control system executes controls of: raising the rotating speed of the prime mover while the transmission is not rotated by the prime mover, to increase the output volume of the hydraulic pump; oil pressure instructing for outputting a plurality of instruction signals of different pressure instruction values to the pressure modulating mechanism while the output volume of the hydraulic pump is increased, to output oil pressures at a plurality of pressure levels; detecting the oil pressure to be modulated and fed to the transmission, at a plurality of pressure levels; and learning and correcting the instruction signals on the basis of the pressure instruction value outputted by the oil pressure instructing control and the oil pressure detected by the oil pressure detecting control.
In the invention, therefore, the output pressure of the hydraulic pump is raised by increasing the rotating speed of the prime mover while the transmission is not rotated by the prime mover. Even with the transmission being stopped, therefore, the oil pressure to be generated by the hydraulic pump or the oil pressure source can be to a pressure at the highest level in the acting state of the transmission. In addition, the signals at the plurality of pressure instruction values are outputted. Without any manipulation to activate the transmission with applying the high pressure to the transmission, therefore, it is possible to generate and detect the oil pressure in the practical state of the transmission and to make the learning correction of the oil pressure.
On the other hand, the hydraulic control system of the invention execute controls of oil pressure instructing for outputting an instruction signal at a predetermined pressure instruction value to an electrically active pressure modulating mechanism to output an oil pressure at a predetermined pressure level; detecting the oil pressure to be modulated and fed to the transmission, at a plurality of pressure levels; learning and correcting the instruction signals on the basis of the pressure instruction value outputted by the oil pressure instructing control and the oil pressure detected by the oil pressure detecting control; and raising the rotating speed of the prime mover when an output timing of the oil pressure instruction signal is detected.
In the hydraulic control system of the invention thus constructed, therefore, when the instruction signal to output the oil pressure at the predetermined level is outputted, the rotating speed of the prime mover is accordingly increased to increase the output volume of the hydraulic pump. As the oil pressure is detected, moreover, the learning and correction of the instruction signal is made on the basis of the detected oil pressure and the pressure instruction value according to the instruction signal. In order to learn the oil pressure, therefore, the oil pressure is retained for the learning by increasing the rotating speed of the prime mover so that the proper oil pressure can be learned.
According to the invention, moreover, there is provided a hydraulic control system for generating an oil pressure from a hydraulic pump by turning a prime mover, as connected to a transmission capable of selecting a non-running shift position transmitting no power and the hydraulic pump, and for outputting an oil pressure instruction signal to an electrically activated pressure modulating mechanism, to modulate the oil pressure generated in the hydraulic pump to an oil pressure according to the instruction signal and to feed the modulated oil pressure to a transmission. The hydraulic control system executes controls of: raising the rotating speed of the prime mover, while the non-running shift position is selected and/or where the vehicle is stopped, to increase the output volume of the hydraulic pump; oil pressure instructing for outputting a plurality of instruction signals of different pressure instruction values to the pressure modulating mechanism while the output volume of the hydraulic pump is increased, to output oil pressures at a plurality of pressure levels; detecting the oil pressure to be modulated and fed to the transmission, at a plurality of pressure levels; and learning and correcting the instruction signals on the basis of the pressure instruction value outputted by the oil pressure instructing control and the oil pressure detected by the oil pressure detecting control.
In the invention, therefore, either while the transmission is not transmitting the power and while the vehicle is stopped, or while the vehicle is stopped, the rotating speed of the prime mover is increased to raise the output pressure of the hydraulic pump. Even while the transmission is stopped, therefore, the oil pressure to be generated by the hydraulic pump or the oil pressure source is as high as the highest level in the acting state of the transmission. In addition, the signals of the plurality of pressure instruction values are outputted so that the generation and detection of the oil pressure in the practical state of the transmission and the learning and correction of the oil pressure can be performed without any operation to activate the transmission with applying the high pressure to the transmission.
In the invention, on the other hand, at the rotating speed raising control, the rotating speed of the prime mover can be raised to a predetermined rotating speed larger than the rotating speed at which the hydraulic pump outputs an oil pressure higher than the highest pressure used in the transmission. Here, the predetermined rotating speed can be made to exceed the idling speed when the vehicle is stopped.
With this construction, therefore, the pressure of the oil pressure source at the time of the learning control of the oil pressure does not disperse so that a highly precise learning control can be made.
In the invention, moreover, the hydraulic control system can further executed a learning instruction control for outputting instructions to perform, for a predetermined time period: the increase in the rotating speed of the prime mover by the rotating speed raising control; the output of the instruction signal of the pressure instruction value to the pressure modulating mechanism by the oil pressure instructing control; the detection of the oil pressure by the oil pressure detecting control; and the learning and correction of the instruction signals by the learning and correction control. Here, the predetermined time period may be a term by the time when the vehicle is delivered to a purchaser.
With this construction, therefore, the learning and correction of the oil pressure in the inactive state of the transmission is executed for the predetermined time period so that the learning and correction of the oil pressure can be made easily without affecting the actions of the transmission.
In the invention, moreover, the predetermined time period can be a term before a vehicle having the transmission mounted thereon is shipped from a factory.
With this construction, therefore, the rotating speed of the prime mover is increased in the manufacturing factory of the vehicle so that its operations/works can be easily done. As a result, the learning and correction of the oil pressure can be easily operated in an improved high correction precision.
The hydraulic control system can further execute rounding oil pressure instructing control for outputting an instruction signal to instruct an oil pressure higher than that to be used for the learning and correction, before the oil pressure instructing control outputs the instruction signal for instructing the oil pressure to be used in the learning and correction.
With this construction, therefore, the pressure modulating mechanism is once activated, and the learning and correction of the oil pressure is made after the actions of the mechanism are smooth, so that the learning correction can be precisely made.
The hydraulic control system of the invention can further execute correction control for correcting the pressure instruction value for the pressure modulating mechanism in an oil pressure increasing side, before the output volume of the hydraulic pump is increased by the rotating speed raising control to make the learning and correction, thereby to feed an oil pressure higher than the pressure instruction value to the transmission.
With this construction, therefore, the oil pressure to be fed to the transmission before the completion of the learning and correction of the oil pressure is higher than the pressure instruction value. In other words, the transmission is fed with an oil pressure which is shifted to a higher level than the estimated oil pressure. Therefore, the contact pressure at the frictionally contacting portions for transmitting the torque is so sufficiently higher than the transmission torque so that the trouble such as the slippage can be prevented in advance.
In the hydraulic control system of the invention, moreover, the pressure modulating mechanism can have a non-modulating range in which the output oil pressure accompanying the change in the instruction signal does not change, and the oil pressure instructing control can output an oil pressure other than that in the non-modulating range, as the pressure instruction value.
With this construction, therefore, the learning control is not made in the non-modulating pressure range in which no correlation holds between the pressure instruction value and the generated pressure. It is, therefore, possible to prevent the learning and correction precision and the oil pressure control precision in advance from any deterioration.
Moreover, the hydraulic control system of the invention can further execute decision control for deciding that at least one of the rotating speed of the prime mover and its fluctuation is within predetermined ranges which are preset according to the individuals, and the oil pressure instructing control can output the plurality of instruction signals where the rotating speed of the prime mover or its fluctuation falls within the individual predetermined ranges.
With this construction, therefore, the learning and correction of the oil pressure is made while the prime mover and the hydraulic pump driven by the former are sufficiently high and stable in their rotating speeds, so that the control precision of the oil pressure can be improved.
According to the invention, on the other hand, there is provided a hydraulic control system for generating an oil pressure by turning a prime mover connected to a hydraulic pump and for outputting an oil pressure instruction signal to an electrically activated pressure modulating mechanism, to modulate the oil pressure generated in the hydraulic pump to an oil pressure according to the instruction signal and to feed the modulated oil pressure to a transmission. The hydraulic control system executes controls of: detecting the speed of a vehicle having the transmission mounted thereon; oil pressure instructing control for outputting an instruction signal at a predetermined pressure instruction value to the pressure modulating mechanism, when the vehicle speed is higher than a predetermined reference vehicle speed and is stable, to output oil pressures at a plurality of pressure levels; detecting the oil pressure to be modulated and fed to the transmission; and learning and correcting the instruction signals on the basis of the pressure instruction value outputted by the oil pressure instructing control and the oil pressure detected by the oil pressure detecting control.
In the hydraulic control system thus constructed, therefore, while the vehicle is running at a stable speed higher than a predetermined value, the instruction signal of the predetermined pressure instruction value is outputted, and the oil pressure is detected so that the learning and correction of the instruction oil pressure is made on the basis of the pressure instruction value and the detected pressure. As a result, it is possible to correct the deterioration in the control precision of the oil pressure due to the aging of the control device such as the pressure modulating mechanism. Especially if the learning and correction are made while the rotations of the prime mover are stable at a predetermined or higher vehicle speed and during a deceleration, or preferably if the rotating speed of the prime mover is stable and higher than a predetermined value sufficient for the output volume of the hydraulic pump, it is possible to make the learning and correction of the oil pressure highly precisely all over the practical range.
In the hydraulic control system of the invention, on the other hand, the oil pressure instructing control can include a control for outputting an instruction signal at the predetermined pressure instruction value in the rising procedure of output oil pressure of the pressure modulating mechanism, and an instruction signal at the predetermined pressure instruction value in the falling procedure of the output oil pressure of the pressure modulating mechanism, and the oil pressure detecting control can detect an oil pressure according to the pressure instruction value in the rising procedure of the output oil pressure of the pressure modulating mechanism and an oil pressure according to the pressure instruction value in the failing procedure of the output oil pressure of the pressure modulating mechanism.
With this construction, therefore, where the deviation (or hysteresis) is between the oil pressure generated in the rising procedure of the pressure and the oil pressure generated in the falling procedure even for the identical pressure instruction value, the hysteresis can be detected. It is also possible on the basis of the detection result whether the transmission or the hydraulic control system is proper or improper.
In the hydraulic control system of the invention, moreover, the pressure instruction value may include at least any two of the highest pressure value in the using range of the transmission, an average oil pressure value in the ordinary running state which is the most frequent for the vehicle having the transmission mounted thereon, and the lowest pressure value in the using range of the transmission.
With this construction, therefore, the oil pressure in the practical range of the transmission can be learned and corrected over the wide range so that the control precision of the oil pressure is improved.
Moreover, the hydraulic control system of the invention can further execute an inhibition control for inhibiting the learning and correction, where either a deviation between the pressure instruction value and the oil pressure detected by the oil pressure detecting control or the learning and correction based on the pressure instruction value and the oil pressure detected by the oil pressure detecting control is higher than a predetermined value.
With this construction, therefore, where the oil pressure generated deviates largely from the pressure instruction value, it is decided that a mechanical trouble exceeding the individual difference occurs in the pressure modulating mechanism. Therefore, the learning and correction can be inhibited for a mechanical repair.
The above and further objects and novel features of the invention will more fully appear from the following detailed description when the same is read with reference to the accompanying drawings. It is to be expressly understood, however, that the drawings are for the purpose of illustrations only and are not intended as a definition of the limits of the invention.